The present invention relates to substituted phenolic thioether derivatives and more particularly relates to the novel compounds of Formula I which are specific 5-lipoxygenase inhibitors and are useful, for example, as anti-inflammatory and anti-allergy agents.
It is well recognized that arachidonic acid, an essential unsaturated fatty acid, is enzymatically oxygenated to various products, including, prostaglandins, thromboxanes, the 5-, 11-, 12- and 15-hydroxyeicosatetraenoic acids (HETEs, DIHETEs) and hydroperoxyeicosatetraenoic acids (HPETEs) and the leukotrienes, all of which have potent physiological effects. The leukotrienes, which are produced via the 5-lipoxygenase pathway, are the major contributors to the onset of the symptoms of asthma, and mediators for immediate hypersensitivity reaction, inflammation and other allergic responses.
Leukotrienes are found in inflammatory exudates and are involved in the process of cellular invasion during inflammation. The term "leukotrienes" is used as a generic term to describe a class of substances, such as slow-reacting substance (SRS) which is an important mediator in asthma and other hypersensitivity reactions. Immunologically generated SRS is usually referred to as slow-reacting substance of anaphylaxis (SRS-A). SRS-A consists of leukotrienes (LT) known as A.sub.4, B.sub.4, C.sub.4, D.sub.4, and E.sub.4. LTC.sub.4 is at least 100 times more potent than histamine in causing long lasting bronchoconstricting effects. The leukotrienes also increase vascular permeability and cause decreased cardiac output and impaired ventricular contraction. LTB.sub.4 may be an important mediator of inflammation in, for example, inflammatory bowel disease.
Chemotaxis is a reaction by which the direction of migration of cells is determined by substances in their environment. It is one of the major processes bringing leukocytes from the blood to an inflammatory site, whether the inflammation is caused by an infectious agent, allergic challenge, or other pro-inflammatory stimuli. LTB.sub.4 is not only chemotactic for neutrophils and monocytes, but is also highly active in stimulating eosinophil locomotion and possibly that of tumor cells (metastasis). LTB.sub.4 also stimulates calcium influx and aggregation of polymorphonuclear leukocytes and LTB.sub.4 may, thus, play an important role in mediating both acute and chronic inflammation.
Rheumatoid spondylitis is characterized by an acute neutrophil flareup in the joint which is associated with elevated levels of LTB.sub.4. LTB.sub.4 is also present in gouty effusions; and exposure to urate crystals is known to stimulate LTB.sub.4 production by neutrophils. Accordingly, the 5-lipoxygenase inhibitors of the present invention through inhibition of neutrophil attraction and activation in arthritic joints should reduce the protease and oxidative burden believed responsible for joint destruction in arthritic diseases. Examples of such proteases include elastase, cathepsin G., collagenase and the like.
Aspirin and the other non-steroidal anti-inflammatory agents (NSAIDs) such as indomethacin, ibuprofen, fenoprofen, and the like, inhibit the synthesis of prostaglandins via the cyclooxygenase pathway of arachidonic acid metabolism. These prostaglandin synthetase inhibitors generally exhibit anti-inflammatory, anti-pyretic and analgesic activity, and are widely used in the treatment of arthritis. The non-steroidal anti-inflammatory agents can lead to the formation of additional pro-inflammatory derivatives of arachidonic acid produced through the 5-lipoxygenase pathway which play a role in immediate hypersensitivity reactions and also have pronounced inflammatory effects. Administration of the NSAIDs alone can produce allergic reactions including bronchospastic reactivity; skin rashes; syndrome of abdominal pain, fever, chills, nausea and vomiting; and anaphylaxis. For this reason, aspirin and the other non-steroidal anti-inflammatory agents (NSAIDs) are generally contraindicated for patients suffering from asthma or who have previously exhibited allergic sensitivity to aspirin or other NSAIDs. Co-administration of the 5-lipoxygenase inhibitors of this invention with protease inhibitors and/or cyclooxygenase inhibitors may mitigate the untoward side effects of the latter and allow the increased advantageous use of such cyclooxygenase inhibitors.
Prior to the recognition of the significance of the 5-lipoxygenase pathway of arachidonic acid metabolism in allergic reactions and inflammation, the search for effective therapeutic agents was based primarily on those agents which treated the symptoms of allergy and inflammation. There has since been effort to develop new drugs which selectively block the formation of the mediators of these conditions, and the present invention provides new chemical entities which are inhibitors of the 5-lipoxygenase pathway and are useful in the treatment of asthma, rheumatoid arthritis, psoriasis, inflammatory bowel disease, nephritis, vasculitis, adult respiratory distress syndrome (ARDS) and other allergic, hypersensitivity, and inflammatory conditions.
See Bengt Samuelsson, "Leukotrienes: Mediators of Immediate Hypersensitivity Reactions and Inflammation", Science, 220, 568-575 (1983); Michael K. Bach, "Inhibitors of Leukotriene Synthesis and Action", The Leukotrienes, Chemistry and Biology, pp 163-194 (Academic Press, Inc., 1984); C. W. Lee et al., "Human Biology and Immunoreactivity of Leukotrienes", Advances in Inflammation Research, Volume 6, pp 219-225 (Raven Press, New York 1984); Editorial, "Leukotrienes and other Lipoxygenase Products in the Pathogenesis and Therapy of Psoriasis and Dermatoses", Arch. Dermatol, 119, 541-547 (1983); Robert A. Lewis et al., "A Review of Recent Contributions on Biologically active Products of Arachidonate Conversion", Int. J. Immunopharmac., 4, 85-90 (1982); Michael K. Bach, Biochemical Pharmacology, 23, 515-521 (1984); and E. L. Becker, Chemotactic Factors of Inflammation, pp 223-225 (Elsevier Science Publishers V.B., Amsterdam, 1983); P. Sharon, and W. F. Stenson, Gastroenterology, 84, 454 (1984); and M. W. Musch, et al., Science, 217, 1255 (1982).
The present invention provides compounds which block the 5-lipoxygenase metabolic pathway and, therefore, block the formation of the leukotrienes responsible for allergy and inflammation, and represent therapeutic agents which are useful in the treatment of allergic and hypersensitivity reactions and inflammation, alone, or also may be utilized in combination with other lipoxygenase inhibitors or with cyclooxygenase inhibitors such as the non-steroidal anti-inflammtory agents.
Various thioether compounds have been described previously. For example, CA 94 (5): 30290c, CA 76 (19): 109226y and CA 73 (9): 45047u disclose 2,6-bis(1,1-dimethylethyl)-4-(methylthio)phenol and CA 84 (2): 6258w and CA 73 (9): 45057u disclose 2,6-bis(1,1-dimethylethyl)-4-[(1,1-dimethylethyl)thio]phenol, and CA 83 (3): 27876r discloses 2,6-bis(1,1-dimethylethyl)-4-(octylthio)-phenol.
U.S. Pat. Nos. 4,029,812, 4,076,841 and 4,078,084 disclose compounds of the formula ##STR1## comprising 2-(3,5-di-tert-butyl-4-hydroxyphenyl)thio carboxamides where R.sub.1 and R.sub.2 independently represent hydrogen, lower alkyl, lower alkoxy, hydroxy, or lower hydroxyalkyl. The compounds are indicated to be useful in lowering serum cholesterol and triglyceride levels.
A series of thioethers, useful as, for example, polyfunctional antioxidants for polymers, and biologically active substances, obtained by the nucleophilic addition of thiols, including 3,5-di-tert-butyl-4-hydroxythiophenol, and hydrogen sulfide to acrylate derivatives have been described. See Medvedev et al., Izv. Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol., 20, 568-574 (1977). The compounds resulting from the foregoing process have the general formulas RS(CH.sub.2).sub.n X and S(CH.sub.2 CH.sub.2 X).sub.2 in which R is 3,5-di-tert-butyl-4-hydroxyphenyl and X represents, for example, --C.tbd.N, NH.sub.2, CH(OH)CH.sub.2 Cl, OH, COCl, and various carboxy, carboxylate and amide functions. Compounds of formula I according to the present invention or 5-lipoxygenase activity for structurally related compounds are not disclosed.
U.S. Pat. No. 4,153,803 discloses cholesterol-lowering phenoxyalkanoic acid esters of the formula ##STR2## wherein, when Y is sulfur, X is hydrogen, benzyl, benzyloxy, benzylthio, or substituted derivatives thereof; R is hydrogen, halogen, hydroxy, alkyl, or alkoxy; A.sup.1 and A.sup.2 are hydrogen or alkyl; and Z is amine or azacyclohydrocarbyloxy, alkoxy, hydroxy, O--M.sup.+ where M is a cation, cycloalkoxy, tertiaryaminoalkoxy, pivaloyloxyalkoxy or pyridyl-C-alkoxy.